I was talking to a friend of mine about mannerisms in interviews and how distracting they can be. He said they often videotape instructors so the instructors can see their own mannerisms and speech patterns. A recent candidate had wild gestures and a few nervous habits that went beyond hand wringing, finger weaving, or fidgeting.
This candidate would raise his arms, lace his fingers and bring his hands down to his knee as he leaned forward. Sometimes both feet were on the ground, sometimes one leg would be crossed over with that foot resting on the other knee. After getting into this pose, he would lean forward while he spoke. He did this repeatedly and I began to be distracted by his actions rather than listening fully to what he was saying.
These days most people have access to video. It's on your phone, your Flip or your tablet. So set that to "record" and have a friend or family member interview you. Treat the interview seriously, then watch the video. You may be surprised to find that you are doing things you didn't realize you were doing. You may also discover that you are projecting an image you didn't intend to project.
Let friends and family watch the video as well. Take their criticism in a positive manner, make adjustments and then do the exercise again until you look like the person you want to be during every job interview.